Measurements of the heights of a random sample of 100 male s

Measurements of the heights of a random sample of 100 male students at XYZ University showed a mean of 67.45 inches and a standard deviation of 2.93 inches. Find a 99% confidence interval for estimating the mean height of the students.

66.176 ?

Solution

Given a=1-0.99=0.01, Z(0.005) = 2.58 (From standard normal table)

So the lower bound is

xbar - Z*s/vn =67.45 -2.58*2.93/sqrt(100) =66.69406

So the upper bound is

xbar + Z*s/vn =67.45 +2.58*2.93/sqrt(100) =68.20594

Answer: C. 66.694 ?